Many kinds of pumps are known in the art and adaptations have been made for specific applications. Pumps for moving fluids are powered by motors that drive moving components, usually pistons and valves, to produce a force on a fluid that causes it to flow. Valves in such pump systems are generally activated by electromechanical devices such as solenoids and other mechanical components. As one of skill in the art will appreciate, there are countless versions of pumps for many different applications. In the medical device field, e.g., there are peristaltic pumps, diaphragm pumps and centrifuge pumps for delivering blood and other biological fluids for specific purposes. Pumps used in many of today's modern chemical processes, including oil or petroleum refining, food and drug manufacturing and electric generation, rely extensively on a complex interconnection of pumps, piping and valves to effect a particular chemical conversion or mixture. The reliance on multiple dedicated pumps or redundant valve configurations results in complex, expensive systems that require high maintenance and manufacturing costs.
Polymer actuators, requiring no moving parts, are often used in these complex systems to simplify valve operation. A class of actuators, electroactive polymers (EAP—known as artificial muscles), has recently been developed. See, e.g., “Electroactive Polymer (EAP) Activators as an Artificial Muscles” Yoseph ar-Cohen Ed., Society of Photo-Optical Instrumentation Engineers, Publisher (2001). Electroactived polymers reversibly swell or change form when activated. The mechanical force exerted by activated EAP is captured to move components in actuator devices.
U.S. Pat. No. 6,664,718 describes monolithic electroactive polymers that act as transducers and convert electrical energy to mechanical energy. The EAP are used to generate mechanical forces to move components of robots or pumps.
U.S. Pat. No. 6,682,500 describes a diaphragm pump powered by EAP. In this pump, an EAP is positioned beneath a flexible membrane termed a “diaphragm”. As the EAP is activated, it swells and contracts and thereby reversibly moves the diaphragm which in turn displaces liquid in which it is in contact. The diaphragm pump uses check-flow valves to control liquid flow.
U.S. Pat. No. 6,685,442 discloses a valve actuator based on a conductive elastomeric polymer gel. In operation, the conductive gel polymer is activated by an electrolyte solution. By manipulating the potential across the gel, the motion of an elastomeric membrane over the expanding gel and the electrolyte solution can be controlled to act as a “gate” to open or close a fluid channel as a check-valve for that channel.
The use of actuators in pump systems reduces the complexity of system operation. Yet each of the disclosed pumps that incorporate polymeric actuators still requires moving parts and valves. The mechanical complexity, maintenance expense, large size and weight, sterility problems, fluid-contaminating erosion products, chemical incompatibility with certain fluids and often noisy operation, make most pump systems unsuitable for certain purposes.
The foregoing background discussion derives from my published PCT application PCT/US2004/005922 which is incorporated in its entirety, by reference, in which I describe an actuator pumping system that utilizes the force of expanding or deflecting actuators inside a housing of fixed volume to displace liquid through the housing. No moving parts or valves are required. The timed activation of individual actuators causes the actuators to change dimensions at a determined time and sequence and thereby cause the fluid to flow at a certain time and path. More particularly, as described in my aforesaid PCT application, a pump system for moving a fluid comprises an actuator housing having a chamber for housing the fluid, a plurality of contiguous actuators located in the chamber, and activating means for sequentially activating individual actuators. Each actuator, when activated, changes dimensions and exerts a displacing force on the housed fluid.
In preferred embodiments of the invention of my aforesaid PCT application, the actuator housing comprises two or more chambers in fluid connection. In certain instances, the separate chambers may be programmed to displace different segments of fluid at individualized rates and flow paths. The separate chambers may, e.g., be used to modify flow rates of fluids that change viscosity while moving through the housing. In other instances, coordination of flow rate through the separate chambers may be used to subdue any pulsing flow patterns from individual chambers into a smooth continuous fluid flow pattern downstream from the chambers.
The pump may comprise a means for controlling the actuator activating means whereby individual actuators are activated at a determined time. The controller in preferred embodiments is a programmable microprocessor in electrical connection with the activating means. Also, in certain instances, the pump may comprise a sensor means for determining physical properties of the fluid. The sensor is in electrical connection with the controlling means and provides feed-back about the physical state of the fluid to the controlling means. The sensor may, for example, measure changes in pH, viscosity, ionic strength, velocity, pressure or chemical composition of fluid. This feed-back allows the pump to interactively alter fluid flow rate and direction.
In preferred embodiments of the invention of my aforesaid PCT application, the pump moves a fluid at a controlled rate. In these embodiments, the activating means sequentially activates individual contiguous actuators at a selected time. The rate at which the fluid flows depends on the rate of actuator activation and volume displaced by each actuator. Thus, in certain preferred instances, the individual actuators are repeatedly pulsed sequentially at rapid intervals, and liquid is essentially spurted from the housing. In other instances, a first group of contiguous actuators is activated at a certain time and then, while the first group return to their original dimensions, a second group of contiguous actuators is sequentially activated. Repetition of this activation pattern for several times or with more groups of actuators along the fluid flow path causes a volume of fluid to be displaced and eventually to be ejected from the housing. The amount of fluid displaced in a given time is determined by the difference in volume between activated actuators restored activators.
As taught in my aforesaid PCT application, the chamber in the actuator housing should be sufficiently rigid to prevent it being deformed by the force exerted by activated actuators, since the displacing force of the activated actuators requires the chamber to maintain an essentially constant volume. In certain instances, however, as when the pump is to be placed into a small cavity, the actuator housing may be slightly deformable while being inserted.
Other activated pump systems described in the art include Harting in U.S. Pat. No. 6,955,923, who describes a device and method for investigating the flowability of a physiological fluid sample. This claims a device that measures various components of the blood through a pump that comprises an uptake passage for the fluid sample, an actuator device for providing cyclic change in orientation of measuring particles in the fluid sample, and a detector device for detecting the change in orientation of the measuring particles. This device also describes the movement of the fluid through the actuator in a back and forth motion. Systems for moving fluid and measuring components of the blood can be combined with molecule delivery systems within the pumping device. Westberg and Vishnoi described blood processes systems and methods using an actuated and programmable in U.S. Pat. No. 6,949,079 describes a pump system where blood is analyzed and a control and analysis system can make various programmed responses in relation to the blood components. Wilson describes an injection pump and combinatorial reactor method in U.S. Pat. No. 6,902,704 where a pathway in a plurality of injectors move to ingest, store, and discharge fluid. Multifaceted actuators will aid in the flexibility and dynamics of such pumping devices because of their varying physical properties can be manipulated to achieve a wide range of applications.
Most actuator systems described in the prior art comprise Electro Active Polymers (EAPs). Electricity can be used as an activating method for causing the material composing the actuator housing to change shape. The completion of an electrical circuit causes delivery of electrons to the shape changing material, which makes the actuator housing unit move. Once electrically activated, the material will also expand and exert force on the matter being moved through the actuator housing or will contract, relax, and relieve force or pressure from the matter and will keep it in the actuator housing.
Many actuator pumps and devices have described the use of EAPs in their composition. Pelrine, Kornbluh, and Pei described a system of electrocute polymers transducers and actuators in U.S. Pat. No. 6,940,211. The actuator system described a system composed of EAPs where one transducer moved a fluid in one direction as part of a pumping system that might be composed of many transducers. Urano and Kitahara described an EAP actuator and diaphragm pump in U.S. Pat. No. 6,960,864 where a pump is composed of several EAP tubular layers that are connected by a continuity of peripheral surfaces. Pelrine and Kornbluh used master and slave EAPs in U.S. Pat. No. 6,876,135 for a device that converts electrical to mechanical energy, where the device is composed one or two active areas.
Calvert and Liu described the “Freeform Fabrication of Hydrogels” in Acta Materialia (1998), where new kinds of hydrogels that contains multiple layers are able to exhibit multiple properties that will aid in the development of EAP actuators. They outlined a process in which novel hydrogels combine the usage of their structure to obtain certain functionalities with both chemical and thermal materials. They also described “Multilayer Hydrogels as Muscle-like Actuators” in the Journal Advanced Materials (2000) where An actuator was constructed using a combination of cross-linked polyacrylic acid and polyacrylamide hydrogels. The advantage of this particular stacking of polymers resulted in a linear rather than bent motion, which allowed control of water flow through the chamber.
Chemical methods can be used to activate the autonomous pumping and processing actuator system. The material that composes the actuator housing system changes shape upon activation involving a chemical reaction. Processing, mixing, and other reactions and chemical synthesis methods can be accomplished with the addition of heating or cooling elements, allowing temperature sensitive processes and chemical reactions to actuator housing systems. The housing actuator systems can also be used in combination with catalysts and other materials such as oxides or metals to obtain specifically desired chemical results.
Light and other photoactive elements may also be used as the activating method. Using one or more different wavelengths can produce photochemical reactions and processes. This lighted method of activation also causes a physical change in the material composing the actuator housing. These and additional energy sources may also be utilized together to generate the desired chemical or biological reactions and chemistry coupled with sensors to allow process and reaction control feedback and autonomous abilities to the system.
A specific example of an actuator composed of a light activated substance would be an epoxy based formulation of a water soluble amine such as Jeffamine and Poly Ethylene Glycol or EGDE in aqueous solution, by adding a light emitting dopant, dye or photo initiator such as Methylene Blue. The initial aqueous solution in the dye is suspended or polymerized into the epoxy. After the curing process is complete, the polymer is hydrated and swollen with aqueous solution and photo irradiation of the material, which creates a pH change within the hydrated polymer to acid. The acids swell the amines further, and the amount of swelling is tunable by changing ratios and concentrations of the epoxy components and the dye. When the irradiation is stopped, the reaction stops and the polymer relaxes back to its neutral hydrated state, thereby creating an effective photo switch mechanism for a polymer actuator.
To further refine or reverse the switching mechanism a chelator or quenching molecule can be used to reverse or rebalance the polymer at a different wavelength of light. An example of this is the use of Titanium Dioxide in the polymer to oxidize the aqueous solution, and when irradiated it produces oxygen, which can then quench the fluorescence of a dye such as a Tris (4,7-diphenyl-1,10-phenanthroline)ruthenium(II) bis(hexafluorophosphate) complex. There are many additional chemicals and compound molecules that can be used for the switching process such as functionalized dendrimers with amino or other surface groups, chemiluminescent dyes, laser dyes, photochromic dyes, phthalocyanines, porphyrins, fluoropolymers and monomers. This method is also applicable to changing the polymer ions selectivity, allowing the control of the polymers hydrophilic and hydrophobic properties in order to control the polymer swelling.
The various forms of energizing may be visible and non visible light, electrical, chemical, photochemical, electromagnetic, electrochemical, radiation, radio frequency, ultrasonic, temperature can be used in combination to allow various combinations of simultaneous functions. These functions include actuation, chemistry, application, sensing and feed back control, and processing. This allows programmed or autonomous sensing for the alteration or processing of matter in or through the system. Additional non-activated materials such as non activated hydro gels may also be encapsulated in the actuator and may perform functions or store biological fluids, chemical molecules, or cells.